MySQL---DDL+DQL---（四）

三、对数据库表记录进行操作(修改DDL)

1、插入记录：insert

语法：
insert into 表 (列名1,列名2,列名3..) values (值1,值2,值3..);--向表中插入某些列
insert into 表 values (值1,值2,值3..);--向表中插入所有列

mysql> insert into tbl_user(uid,uname,upassword) values(null,'zhangsan','');
Query OK, 1 row affected (0.27 sec)

mysql> select * from tbl_user;
+-----+----------+-----------+
| uid | uname    | upassword |
+-----+----------+-----------+
|   1 | zhangsan | 123       |
+-----+----------+-----------+
mysql> insert into tbl_user values(null,'xiaobing','');
Query OK, 1 row affected (0.06 sec)

mysql> select * from tbl_user;
+-----+----------+-----------+
| uid | uname | upassword |
+-----+----------+-----------+
| 1 | zhangsan | 123 |
| 2 | xiaobing | 456 |
+-----+----------+-----------+
2 rows in set (0.00 sec)

注意：中文插入乱码解决【方式一】修改安装目录的配置文件my.ini;---character-set-server=utf8;【方式二】mysql> set names utf-8;

2、更新记录:update
语法:
update 表名 set 字段名=值,字段名=值 ...;
update 表名 set 字段名=值,字段名=值 ... where 条件;

mysql> select * from tbl_user;
+-----+----------+-----------+
| uid | uname    | upassword |
+-----+----------+-----------+
|   1 | zhangsan | 123       |
|   2 | xiaobing | 456       |
|   3 | 小兵     | 789       |
+-----+----------+-----------+
3 rows in set (0.00 sec)

mysql> update tbl_user set upassword='';
Query OK, 3 rows affected (0.09 sec)
Rows matched: 3  Changed: 3  Warnings: 0
mysql> select * from tbl_user;
+-----+----------+-----------+
| uid | uname    | upassword |
+-----+----------+-----------+
|   1 | zhangsan | 666       |
|   2 | xiaobing | 666       |
|   3 | 小兵     | 666       |
+-----+----------+-----------+
3 rows in set (0.00 sec)
mysql> update tbl_user set upassword='' where uid=3;
mysql> select * from tbl_user;
+-----+----------+-----------+
| uid | uname | upassword |
+-----+----------+-----------+
| 1 | zhangsan | 666 |
| 2 | xiaobing | 666 |
| 3 | 小兵 | 999 |
+-----+----------+-----------+
3 rows in set (0.00 sec)

3、删除记录:delete

语法:
delete from 表名 [where 条件];

mysql> select * from tbl_user;
+-----+----------+-----------+
| uid | uname    | upassword |
+-----+----------+-----------+
|   1 | zhangsan | 999       |
|   2 | xiaobing | 666       |
+-----+----------+-----------+
2 rows in set (0.00 sec)

mysql> delete from tbl_user where uid=1;
Query OK, 1 row affected (0.08 sec)

mysql> select * from tbl_user;
+-----+----------+-----------+
| uid | uname    | upassword |
+-----+----------+-----------+
|   2 | xiaobing | 666       |
+-----+----------+-----------+
注意：删除后uid不会重置！以上是带条件删除，以下是不带条件删除！
　mysql> delete from tbl_user;
  Query OK, 1 row affected (0.07 sec)

  mysql> select * from tbl_user;
  Empty set (0.00 sec)

注意：delete和truncate的区别?
  　　delete 删除的时候是一条一条的删除,它配合事务,可以将删除的数据找回。
  　  truncate 删除，它是将整个表摧毁，然后再创建一张一模一样的表，它的删除数据无法找回！

mysql> select * from tbl_user;
+-----+----------+-----------+
| uid | uname    | upassword |
+-----+----------+-----------+
|   4 | xiaobing | 666       |
|   5 | xiaobing | 666       |
|   6 | xiaobing | 666       |
+-----+----------+-----------+
3 rows in set (0.00 sec)

mysql> start transaction;（开启事务）
Query OK, 0 rows affected (0.08 sec)

mysql> delete from tbl_user;
Query OK, 3 rows affected (0.00 sec)

mysql> select * from tbl_user;
Empty set (0.00 sec)

mysql> rollback;（回滚事务）
Query OK, 0 rows affected (0.08 sec)

mysql> select * from tbl_user;
+-----+----------+-----------+
| uid | uname    | upassword |
+-----+----------+-----------+
|   4 | xiaobing | 666       |
|   5 | xiaobing | 666       |
|   6 | xiaobing | 666       |
+-----+----------+-----------+
3 rows in set (0.00 sec)
mysql> start transaction;（开启事务）
Query OK, 0 rows affected (0.00 sec)

mysql> truncate table tbl_user;
Query OK, 0 rows affected (0.41 sec)

mysql> select * from tbl_user;
Empty set (0.00 sec)

mysql> rollback;（回滚事务）
Query OK, 0 rows affected (0.00 sec)

mysql> select * from tbl_user;
Empty set (0.00 sec)
mysql> insert into tbl_user values(null,'xiaobing','');
Query OK, 1 row affected (0.06 sec)

mysql> select * from tbl_user;（truncate先摧毁表，后重建表！）
+-----+----------+-----------+
| uid | uname | upassword |
+-----+----------+-----------+
| 1 | xiaobing | 666 |
+-----+----------+-----------+
1 row in set (0.00 sec)
注意：delete删除，uid不会重置，不清空auto_increment记录数。！而使用truncate操作，uid会重置，auto_increment 将置为零，重新开始。！

四、查询操作（DQL 简单查询）

1、创建商品表，准备数据！

mysql> create table product(
    -> pid int primary key auto_increment,
    -> pname varchar(20),
    -> price double,
    -> pdate timestamp
    -> );
Query OK, 0 rows affected (0.70 sec)

mysql> desc product;
+-------+-------------+------+-----+-------------------+-----------------------------+
| Field | Type        | Null | Key | Default           | Extra                       |
+-------+-------------+------+-----+-------------------+-----------------------------+
| pid   | int(11)     | NO   | PRI | NULL              | auto_increment              |
| pname | varchar(20) | YES  |     | NULL              |                             |
| price | double      | YES  |     | NULL              |                             |
| pdate | timestamp   | NO   |     | CURRENT_TIMESTAMP | on update CURRENT_TIMESTAMP |
+-------+-------------+------+-----+-------------------+-----------------------------+
4 rows in set (0.05 sec)
#自动增长列：auto_increment,要求：1.必须整形(int) 2.必须键(主键)
mysql> insert into product values (null,'小兵',0.03,null)
Query OK, 1 row affected (0.10 sec)

mysql> insert into product values (null,'小王',33,null);
Query OK, 1 row affected (0.07 sec)

mysql> insert into product values (null,'小赵',-50,null);
Query OK, 1 row affected (0.11 sec)

2、查询操作，语法:select [distinct] *| 列名,列名 from 表名 [where条件]

2.1 查询所有
mysql> select * from product;
+-----+--------+-------+---------------------+
| pid | pname | price | pdate |
+-----+--------+-------+---------------------+
| 1 | 小兵 | 0.03 | 2019-01-28 15:48:46 |
| 2 | 小王 | 33 | 2019-01-28 15:49:11 |
| 3 | 小赵 | -50 | 2019-01-28 15:49:32 |
+-----+--------+-------+---------------------+
3 rows in set (0.05 sec)

2.2 查询商品名称和商品价格
mysql> select pname,price from product;
+--------+-------+
| pname | price |
+--------+-------+
| 小兵 | 0.03 |
| 小王 | 33 |
| 小赵 | -50 |
+--------+-------+
3 rows in set (0.00 sec)

2.3 查询所有商品信息使用表别名！
mysql> select * from product as p;
+-----+--------+-------+---------------------+
| pid | pname | price | pdate |
+-----+--------+-------+---------------------+
| 1 | 小兵 | 0.03 | 2019-01-28 15:48:46 |
| 2 | 小王 | 33 | 2019-01-28 15:49:11 |
| 3 | 小赵 | -50 | 2019-01-28 15:49:32 |
+-----+--------+-------+---------------------+
3 rows in set (0.00 sec)

mysql> select * from product p;（as可以省略）
+-----+--------+-------+---------------------+
| pid | pname | price | pdate |
+-----+--------+-------+---------------------+
| 1 | 小兵 | 0.03 | 2019-01-28 15:48:46 |
| 2 | 小王 | 33 | 2019-01-28 15:49:11 |
| 3 | 小赵 | -50 | 2019-01-28 15:49:32 |
+-----+--------+-------+---------------------+
3 rows in set (0.00 sec)

2.4 查询商品名使用别名！

mysql> select pname as p from product;
+--------+
| p |
+--------+
| 小兵 |
| 小王 |
| 小赵 |
+--------+
3 rows in set (0.00 sec)

2.5 去掉重复值（按照价格）
mysql> select * from product;
+-----+--------+-------+---------------------+
| pid | pname | price | pdate |
+-----+--------+-------+---------------------+
| 1 | 小兵 | 0.03 | 2019-01-28 15:48:46 |
| 2 | 小王 | 33 | 2019-01-28 15:49:11 |
| 3 | 小赵 | -50 | 2019-01-28 15:49:32 |
| 4 | 小王 | 33 | 2019-01-28 16:16:45 |
+-----+--------+-------+---------------------+
4 rows in set (0.00 sec)

mysql> select distinct(price) from product;
+-------+
| price |
+-------+
| 0.03 |
| 33 |
| -50 |
+-------+
3 rows in set (0.06 sec)

2.6 将所有的价格+10，进行展示：
mysql> select pname,price+10 from product;
+--------+----------+
| pname | price+10 |
+--------+----------+
| 小兵 | 10.03 |
| 小王 | 43 |
| 小赵 | -40 |
| 小王 | 43 |
+--------+----------+
4 rows in set (0.04 sec)

五、查询操作（DQL 条件查询）

1、查询名称为小王的商品信息

mysql> select * from product where pname='小王';
+-----+--------+-------+---------------------+
| pid | pname  | price | pdate               |
+-----+--------+-------+---------------------+
|   2 | 小王   |    33 | 2019-01-28 15:49:11 |
|   4 | 小王   |    33 | 2019-01-28 16:16:45 |
+-----+--------+-------+---------------------+
2 rows in set (0.08 sec)

2、查询商品价格>0元的所有的商品信息　

mysql> select * from product where price>0;
+-----+--------+-------+---------------------+
| pid | pname  | price | pdate               |
+-----+--------+-------+---------------------+
|   1 | 小兵   |  0.03 | 2019-01-28 15:48:46 |
|   2 | 小王   |    33 | 2019-01-28 15:49:11 |
|   4 | 小王   |    33 | 2019-01-28 16:16:45 |
+-----+--------+-------+---------------------+
3 rows in set (0.03 sec)

3、查询商品价格带有“赵”字的商品信息；（模糊查询）

mysql> select * from product where pname like '%赵%';
+-----+--------+-------+---------------------+
| pid | pname  | price | pdate               |
+-----+--------+-------+---------------------+
|   3 | 小赵   |   -50 | 2019-01-28 15:49:32 |
+-----+--------+-------+---------------------+
1 row in set (0.04 sec)

4、查询商品ID在（1，3，5）范围内的所有商品；

mysql> select * from product where pid in (1,3,9);
+-----+--------+-------+---------------------+
| pid | pname  | price | pdate               |
+-----+--------+-------+---------------------+
|   1 | 小兵   |  0.03 | 2019-01-28 15:48:46 |
|   3 | 小赵   |   -50 | 2019-01-28 15:49:32 |
+-----+--------+-------+---------------------+
2 rows in set (0.04 sec)

5、查询名称为小王并且（and）ID为4的商品信息

mysql> select * from product where pname='小王' and pid=4;
+-----+--------+-------+---------------------+
| pid | pname  | price | pdate               |
+-----+--------+-------+---------------------+
|   4 | 小王   |    33 | 2019-01-28 16:16:45 |
+-----+--------+-------+---------------------+
1 row in set (0.04 sec)

注意参考补充：